How physical parameterizations can modulate internal variability in a regional climate model

par Julien Crétat et Benjamin Pohl

accepté le 30 août dans la revue Journal of the Atmospheric Sciences

We analyze here to what extent the internal variability simulated by a regional climate model is sensitive to its physical parameterizations. The influence of two convection schemes is quantified over Southern Africa, where convective rainfall predominates. Internal variability is much larger with Kain-Fritsch scheme than for Grell-Dévényi at both the seasonal, intraseasonal and daily timescales, and from the regional to the local (grid-point) spatial scales. Phenomenological analyses reveal that the core (periphery) of the rain-bearing systems tends to be highly (weakly) reproducible, showing that it is their morphological features that induce the largest internal variability in the model. In addition to the domain settings and the lateral forcing conditions extensively analyzed in the literature, the physical package appears thus as a key factor that modulates the reproducible and irreproducible components of regional climate variability.

Crétat J & Pohl B, 2011: How physical parameterizations can modulate internal variabilityin a regional climate model. J Atmos Sci, published on line. doi:10.1175/JAS-D-11-0109.1

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How physical parameterizations can modulate internal variability in a regional climate model

par Julien Crétat et Benjamin Pohl

accepté le 30 août dans la revue Journal of the Atmospheric Sciences

We analyze here to what extent the internal variability simulated by a regional climate model is sensitive to its physical parameterizations. The influence of two convection schemes is quantified over Southern Africa, where convective rainfall predominates. Internal variability is much larger with Kain-Fritsch scheme than for Grell-Dévényi at both the seasonal, intraseasonal and daily timescales, and from the regional to the local (grid-point) spatial scales. Phenomenological analyses reveal that the core (periphery) of the rain-bearing systems tends to be highly (weakly) reproducible, showing that it is their morphological features that induce the largest internal variability in the model. In addition to the domain settings and the lateral forcing conditions extensively analyzed in the literature, the physical package appears thus as a key factor that modulates the reproducible and irreproducible components of regional climate variability.

Crétat J & Pohl B, 2011: How physical parameterizations can modulate internal variabilityin a regional climate model. J Atmos Sci, published on line. doi:10.1175/JAS-D-11-0109.1